From MozillaZine Knowledge Base

MHTML, a standard for preserving an entire web page and all inline graphics, links, applets etc. In a single file; although supported by Internet Explorer, currently remains unimplemented in Mozilla.

Please see the following open bugs:

• Save as rfc 2557 MHTML; complete webpage in one file - Bug 40873
• Full rfc2557 MHTML multipart/related support in BROWSER - Bug 18764

Although there does exist an extension, that partially supports the MHTML standard, along with its own method for archiving entire web pages.

Available for both the Mozilla Suite/SeaMonkey and Firefox:

• maf

Further information on the MHTML format/standard can be located here:

• MSDN Library - MIME Encapsulation of Aggregate HTML Documents (MHTML)